Stain resisting wrought article



Patented Aug. 8, 1933 PATENT OFFICE 1,920,953' I STAIN RESISTING WROUGHT ARTICLE Frederick M. Becket, New York, N. Y., assignor to Electro Metallurgical Company, a Corporation of West Virginia No Drawing.

Application March 14, 1930 Serial No. 435,957

6 Claims.

The invention relates to articles fabricated from stain-resisting alloys having the very high degree of workabilitynecessary to adapt them to deep-drawing operations.

For purposes which require a stain-resisting metal of fairly high strength and moderate cost, the usual materials at the present time are alloys consisting principally of iron, but containing enough chromium to impart the desired stability of surface. As is well known, these alloys (the carbon percentage being sufficiently low) possess to a remarkable degree the ability to withstand various corrosive influences. It has been found that the capacity of such alloys for deep-drawing 15 can be markedly improved by an addition of nickel, and low-carbonalloys containing approximately 18% of chromium and 8% to 14% of m'ckel, with most of the balance iron, are the best deep-drawing alloys of this class now in com- 20 mercial use.

The alloys with which the present invention is concerned are adapted to the same class of uses as the iron-chromiumnickel alloys referred to Whereas the iron-chromium-nickel alalloys should contain at least about 16% ofv chromium, and at least about of manganese. The upper limit of the chromium range contemplatedherein is about 22%. As a rule I prefer to place the chromium percentage between 17% and 21%. With the chromium in the vicinity of 20%, at least about 6% of manganese is desirable. resistance, Erichsen value and deep-drawing properties. The maximum effect in this direction appears to be attained when the manganese content reaches or so, but higher percentages of manganese, up to at least have no detrimental effect, and are quite unobjectionable unless on economic grounds; Taking all factors into account, a manganese content of 8% to 12% is preferred for most purposes? In the softest and most ductile grades of the alloys under discussion, carbon is not an essential constituent, and it is present only because it is commercially impossible completely to exclude it. Alloys with less than 0.12% carbon are espec ally suitable for some uses, and this figure may be added to the metal, as in standard metallurgical practice, and doubtless there are other elements which may be present in greater or smaller proportion without destroying the useful properties of the metal, or may even improve it for certain purposes. In the following table certain of the properties of specific alloys in the wrought condition are shown:

The manganese improves the shock Analysis Izod impact Ench' Heat treatment sen foot value Cr Mn 0 pounds Pct. Pct. Pet. 17.88 8.26 0.07 Heated5min. at 1050 C. and

water quenched 112.0 10.35 Heated 5 min. at 1050 C d air cooled 77.0 10. 80 17. 55 10. 48 0.07 Heated 5 min. at 1l50 water quenched 112.0 10.10 Heated 5 min. at 1150 C. and

air cooled 85.0 9. 40 18.99 12. 41 0. 08 Heated 5 min. at 1150 C. and

' water quenched 119.5 8.80

Heated 5 min. at 1150 C. and air cooled 72.0 8.60 17. 54 14. 77 0. 09 Heated 5 min. at 1150 C. and

water quenched 120.0 10.00 Heated 5 min. at 1150 C. and

air cooled 115.5 9.20 18.34 11. 75 0. 18 Heated 5 min. at 1150 C. and

water quenched 120.0 10.6 Heated 5 min. at 1150 C. and

air cooled 35.5 10.2

Each of the alloys was subjected, in both the quenched and the air-cooled conditions, to other physical tests as indicated below. The ranges of the numbers obtained were as follows:

Yield point 48,000 to 62,000 lbs.

per. sq. in. Maximum stress 89,800 to 126,000 lbs.

per. sq. in. Elongation in 2 inches 25% to 48% Reduction of area 25.1% to 70.0%

The Brinell numbers fall between 149 and 166 except in the case o the last alloy in the table, containing 0.18% carbon. It registered 187 as quenched and 196 as air-cooled. Each alloy was also subjected to the Erichsen test without previous heat-treatment, i. e. as rolled. The lowest value recorded was 8.75.

When immersed in cold dilute nitric acid (20 cc. 68% 'HNO:+80 cc. water), polished samples of the various alloys did not in any case lose as much as 0.0001 grams per square centimeter per hour.

Polished samples of the tabulated alloys were in no case afiected by the standard salt spray test in 7 days; and when subjected to the Brearley test with copper sulphate solution, no sample precipitated a visible deposit of copper.

It has already been indicated in the prior art that certain iron-chromium manganese alloys are forgeable, and that certain alloys composed of these elements are stain-resistant and ductile after heating and quenching. It will of course be understood that a metal may be truly said to be ductile even though it is practically devoid of deep-drawing properties. Deep-drawing requires a high degree of ductility, combined with toughness and strength, and in the investigation of a new alloy the possession of deep-drawing quality can only be shown by actual trial, regardless of the behavior of the metal in any usual physical test. Ai'ortiori, forging being the simplest form of metal working and deep-drawing one of the most diflicult forms, forgeability is by no means invariably accompanied by deep-drawing properties. So far as I am aware, there is no published statement that any stain-resisting iron-chromium-manganese alloy possesses deep-drawing properties, 1101715 there any published statement that any such alloy can be rendered ductile without quenching. The alloys of the present invention, in the air-cooled condition, have deepdrawing properties comparable with those of the most workable stain-resisting iron-chromiumnickel. alloys when the latter have been heattreated in the manner which' influences their workability most favorably.

An important; advantage of the iron-chromium-manganese alloys described herein, vfrom a commercial point of view, is that very little difllculty is encountered in casting them into clean ingots. With the stain-resisting iron-chromium-nickel alloys, clean metal is only consistently obtained by those thoroughly familiar with their peculiarities, and only by the most careful work. As will be readily understood, inclusions in-the metal are highly detrimental resistance.

I claim:-

1. A stain-resisting article having properties imparted by deep-drawing and by cooling from a temperature between about 1050 C. and about to its stain 1150 C. said article being composed of an alloy obtaining iron, chromium, manganese, and carbon; and said alloy having substantially the composition: 16% to 22% chromium, 6% to 14% manganese, not more than about 0.3% carbon, remainder iron.

2. An article having properties imparted by air-cooling from a temperature between about 1050 C. and about 1150 C.; said properties including an Erichsen number greater than about 8.5, and stain-resistance; said article being composed of an alloy containing iron, chromium, manganese, and carbon; and said alloy having substantially the composition: 16% to 22% chromium, 6% to 14% manganese, not more than about 0.3% carbon, remainder iron.

3. Method of producing stain-resisting, shockresisting, ductile articles, which comprises deepdrawing an alloy containing iron, chromium, manganese, and carbon in substantially the proportions: 16% to 22% chromium, 6% to 14% manganese, not more than about 0.3% carbon, remainder iron and small amounts of incidental impurities; heating the deformed alloy to a temperature between about 1050 C. and about 1150 0.; and thereafter cooling the alloy.

4. Method of producing stain-resisting, shockresisting articles having an Erichsen number greater than about 8.5, which comprises deepdrawing an iron-chromium-manganese-carbon alloy having substantially the composition: 16% to 22% chromium, 6% to 14% manganese, not more than about 0.3% carbon, remainder iron; heating said alloy to a temperature between about 1050 C. and about 1150 C.; and thereafter quenching the alloy.

5. An article having properties imparted by deep-drawing and by rapid cooling from a temperature between about 1050 C. and about 1150 C., said properties including an Erichsen number greater than about 8.5, and stain-resistance; said article being composed of an alloy containing iron, chromium, manganese, and carbon; and said alloy having substantially the composition: 16% to 22% chromium, 6% to 14% manganese, not more than about 0.3% carbon, remainder iron.

6. A stain-resistant deep-drawn article composed of an alloy steel having substantially the composition: 17% to 21% cromium, 6% to 14% manganese, carbon, the carbon content being not more than about 0.12%, the balance iron; which steel has been rapidly cooled from a temperature between about 1050 C. and 1150 C. 

